/*
 * Copyright (C) 2012 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.volley.toolbox;

import android.content.Context;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager.NameNotFoundException;
import android.net.http.AndroidHttpClient;
import android.os.Build;

import com.android.volley.Network;
import com.android.volley.RequestQueue;

import java.io.File;

/**
 * Volley框架特点：
 * 适用于频繁请求而每次请求数据量不会很大；
 * 在请求的基础上做了磁盘缓存；
 * 防止多次相同请求浪费资源；
 * 提供String、Json、图片异步下载；
 * 网络请求的优先级处理；
 * 图片请求无需担心生命周期问题。
 * Volley框架使用：
 */
public class Volley
{
	
	/** Default on-disk cache directory. */
	private static final String DEFAULT_CACHE_DIR = "volley";
	
	/**
	 * Creates a default instance of the worker pool and calls {@link RequestQueue#start()} on it.
	 * You may set a maximum size of the disk cache in bytes.
	 * @param context A {@link Context} to use for creating the cache dir.
	 * @param stack An {@link HttpStack} to use for the network, or null for default.
	 * @param maxDiskCacheBytes the maximum size of the disk cache, in bytes. Use -1 for default size.
	 * @return A started {@link RequestQueue} instance.
	 */
	public static RequestQueue newRequestQueue(
			Context context,
			HttpStack stack,
			int maxDiskCacheBytes )
	{
		File cacheDir = new File( context.getCacheDir(), DEFAULT_CACHE_DIR );
		
		String userAgent = "volley/0";
		try
		{
			String packageName = context.getPackageName();
			PackageInfo info = context.getPackageManager().getPackageInfo( packageName, 0 );
			userAgent = packageName + "/" + info.versionCode;
		}
		catch( NameNotFoundException e )
		{
		}
		
		if( stack == null )
		{
			if( Build.VERSION.SDK_INT >= 9 )
			{
				stack = new HurlStack();
			}
			else
			{
				// Prior to Gingerbread, HttpUrlConnection was unreliable.
				// See: http://android-developers.blogspot.com/2011/09/androids-http-clients.html
				stack = new HttpClientStack( AndroidHttpClient.newInstance( userAgent ) );
			}
		}
		
		Network network = new BasicNetwork( stack );
		
		RequestQueue queue;
		if( maxDiskCacheBytes <= -1 )
		{
			// No maximum size specified
			queue = new RequestQueue( new DiskBasedCache( cacheDir ), network );
		}
		else
		{
			// Disk cache size specified
			queue = new RequestQueue( new DiskBasedCache( cacheDir, maxDiskCacheBytes ), network );
		}
		
		queue.start();
		
		return queue;
	}
	
	/**
	 * Creates a default instance of the worker pool and calls {@link RequestQueue#start()} on it.
	 * You may set a maximum size of the disk cache in bytes.
	 * @param context A {@link Context} to use for creating the cache dir.
	 * @param maxDiskCacheBytes the maximum size of the disk cache, in bytes. Use -1 for default size.
	 * @return A started {@link RequestQueue} instance.
	 */
	public static RequestQueue newRequestQueue(
			Context context,
			int maxDiskCacheBytes )
	{
		return newRequestQueue( context, null, maxDiskCacheBytes );
	}
	
	/**
	 * Creates a default instance of the worker pool and calls {@link RequestQueue#start()} on it.
	 * @param context A {@link Context} to use for creating the cache dir.
	 * @param stack An {@link HttpStack} to use for the network, or null for default.
	 * @return A started {@link RequestQueue} instance.
	 */
	public static RequestQueue newRequestQueue(
			Context context,
			HttpStack stack )
	{
		return newRequestQueue( context, stack, -1 );
	}
	
	/**
	 * Creates a default instance of the worker pool and calls {@link RequestQueue#start()} on it.
	 * @param context A {@link Context} to use for creating the cache dir.
	 * @return A started {@link RequestQueue} instance.
	 */
	public static RequestQueue newRequestQueue( Context context )
	{
		return newRequestQueue( context, null );
	}
	
}

